1. Technical Field
The present invention relates to a position detecting sensor, which is disposed so as to be superposed on a display surface of a display device such as a Liquid Crystal Display (LCD) device or the like, in order to detect a position where an input manipulation is carried out by an indication body, and a position detector that incorporates such position detecting sensor.
2. Description of the Related Art
A position detector for detecting a position indicated by an indication body, such as a finger or a pen, is well known. Various types of position detecting systems may be used in the position detector, such as a resistance film system, an electromagnetic induction system, and a capacitive system. The capacitive system includes two sub-types: a Surface Capacitive Type; and a Projected Capacitive Type. With both the Surface Capacitive Type and the Projected Capacitive Type, a change in a capacitive coupling state between a sensor electrode and an indication body is detected, to thereby detect a position indicated by the indication body.
For example, Patent Document 1 (Japanese Patent Laid-Open No. 2009-9249) discloses a position detector utilizing the capacitive system and having a construction including a two-dimensional capacitive sensor, that is, a construction including an X-axis sensor trace (sensor conductor) and a Y-axis sensor trace (sensor conductor). The X-axis sensor trace and the Y-axis sensor trace, each composed of a light-permeable transparent conductor, are formed on a light-permeable base member, for example, a transparent substrate such as a glass plate. Such construction is based on the assumption that the sensor of the position detector disclosed in Patent Document 1 is disposed so as to be superposed on a display surface of a display device.
For the purpose of detecting a position in an X-axis direction (in a transverse direction), the X-axis sensor traces (each extending in the Y-axis direction) are provided at predetermined intervals in the X-axis direction on the transparent substrate. Also, the X-axis sensor traces have such a shape that plural diamond-shaped transparent conductors are continuously connected to one another in the Y-axis direction (in the longitudinal direction). In addition, for the purpose of detecting a position in the Y-axis direction, the Y-axis sensor traces (each extending in the X-axis direction) are disposed at predetermined intervals in the Y-axis direction on the transparent substrate. The Y-axis sensor traces have such a shape that plural diamond-shaped transparent conductors are continuously connected to one another in the X-axis direction.
The diamond-shaped conductors of the X-axis sensor traces and the diamond-shaped conductors of the Y-axis sensor traces do not overlap each other, and the X-axis sensor traces and the Y-axis sensor traces are combined with each other in a state of being electrically independent of each other, whereby a two-dimensional capacitive sensor is constructed on the transparent substrate. Therefore, the two-dimensional capacitive sensor comes to have a pattern shape, in which the diamond-shaped transparent conductors are uniformly disposed on the transparent substrate. As a result, approximately uniform light permeability can be obtained over the entire transparent substrate.
The two-dimensional capacitive sensor disclosed in Patent Document 1 is a sensor utilizing a so-called line detection system, with which a change in capacitance in any of the plural X-axis sensor traces is detected to thereby detect a position of a finger or a position indicator in the X-axis direction, and a change in capacitance in any of the plural Y-axis sensor traces is detected to thereby detect a position of the finger or the position indicator in the Y-axis direction.
On the other hand, another position detector is proposed, which utilizes a system called a cross-point capacitive system, which has been developed based on the projected capacitive system. FIG. 9 shows a schematic structure surrounding a sensor portion of the position detector utilizing the cross-point capacitive system.
As shown in FIG. 9, the sensor portion of the position detector utilizing the cross-point capacitive system is constructed in such a way that plural upper electrodes Ex each extending, for example, in a Y-axis direction (in a longitudinal direction) on an indication input surface and plural lower electrodes Ey each extending in an X-axis direction (in a transverse direction) are disposed at predetermined intervals in the X-axis direction and in the Y-axis direction, respectively, so as to form right angles with each other with a slight space provided therebetween. In this case, predetermined capacitance Co (fixed capacitance) is formed at a position (at a cross-point), at which each upper electrode Ex and the corresponding lower electrode Ey intersect with each other.
At a position where an indication body 100, such as a position indicator held by a user or a finger of the user, comes close to or in contact with an indication input surface, capacitance Cf is formed between the indication body and the electrodes Ex and Ey corresponding to the position. The indication body 100 is electrically connected through the user's body to the ground via predetermined capacitance Cg. As a result, due to the presence of both of the capacitances Cf and Cg, the shifting amount of electric charge between the upper electrode Ex and the lower electrode Ey is changed at the position indicated (pointed to) by the indication body 100. With the position detector utilizing the cross-point capacitive system, the change in the shifting amount of electric charge is detected, to thereby specify the position within the indication input surface indicated by the indication body 100.
For example, the lower electrode Ey is used as a transmission electrode and a predetermined signal is supplied to the lower electrode Ey, and the upper electrode Ex is used as a reception electrode. Then, a change in current in a received signal from the reception electrode is detected, to thereby detect the change in the shifting amount of electric charge.
When the position detector utilizing the cross-point capacitive system is disposed so as to be superposed on a display surface of an LCD, an organic EL display device or the like, the upper electrode Ex and the lower electrode Ey are formed in such a way that conductive patterns each having a given width and light permeability and, for example, composed of an Indium Tin Oxide (ITO) film extend in the Y-axis direction and in the X-axis direction, respectively, and are disposed on a surface of a light-permeable base member, for example, a transparent glass substrate or the like.
In this case, unlike the line detection system sensor disclosed in Patent Document 1 described above, in the position detecting sensor utilizing the cross-point capacitive system, areas exist in which no light-permeable electrode is formed, in rectangular areas defined by two adjacent upper electrodes Ex and two adjacent lower electrodes Ey. For this reason, since the area in which no light-permeable electrode is formed is different in light permeability from a portion in which the light-permeable conductive pattern is formed, it becomes difficult to obtain uniform light permeability over the entire sensor area (for the purpose of ease in viewing the display surface).
In order to solve this problem, a sensor utilizing a cross-point capacitive system is disclosed in paragraphs [0115] to [0120], and FIGS. 18 and 19 of Patent Document 2 (Japanese Patent Laid-Open No. 2011-3035), in which a dummy pattern 114 made of a light-permeable material, for example, the same ITO film as used to form each of the upper electrodes 110 and lower electrodes 112, is disposed in a rectangular area surrounded by the adjacent upper electrodes 110 and the adjacent lower electrodes 112. In this case, the dummy pattern 114 is electrically independent of any of the upper electrodes 110 and the lower electrodes 112, and is in an electrically floating state (in a floating state). According to the position detecting sensor disclosed in Patent Document 2, due to the presence of the dummy pattern disposed close to each of the upper electrode 110 and the corresponding lower electrode 112, it is possible to achieve uniform optical characteristics by suppressing non-uniformity of transmittance.
In the position detecting sensor utilizing the cross-point capacitive system as described above, plural upper electrodes and plural lower electrodes are disposed linearly in the X-axis direction (in the transverse direction) and in the Y-axis direction (in the longitudinal direction), respectively, to cross each other at right angles on the light-permeable substrate, to thereby form a sensor pattern having a so-called grid pattern. For the purpose of obtaining uniform light permeability over the entire sensor area, dummy patterns are provided in the individual areas defined by the plural upper electrodes and the plural lower electrodes, with a predetermined space provided between the dummy pattern and each of the upper electrodes and the lower electrodes.
For this reason, when the position detecting sensor is disposed so as to be superposed on the screen of the display device such as the LCD, possibly a so-called Moire effect may result between display pixels disposed in the X-axis direction (in the transverse direction) and in the Y-axis direction (in the longitudinal direction) in the display device concerned, and the upper electrodes, the lower electrodes and the dummy patterns, and thus light-and-dark Moire fringes (or simply Moire) may be generated in a displayed image.
Patent Document 3 (U.S. Published Application No. 2009/0273577A1) discloses the invention that can either decrease or prevent the Moire effect between the sensor electrodes of a position detector and the pixel disposition in a display device.
Specifically, as shown in FIG. 10, in a display surface of a display device 602, sub-pixels R, G, and B (corresponding to the three primary colors: red; green; and blue) are repetitively disposed in order in the X-axis direction (in the transverse direction). The disposition in the X-axis direction is also repeated in the Y-axis direction (in the longitudinal direction), whereby display pixels are two-dimensionally disposed. In this case, the sub-pixels corresponding to the same color are disposed in a line in the Y-axis direction, and thus it is known that the Moire effect may easily result between the disposition of the pixels in the Y-axis direction, and the electrodes in the Y-axis direction in the position detecting sensor.
Patent Document 3 discloses a position detecting sensor 600, which is superposed on the display surface of the display device 602 and includes a transmission electrode 604 and a reception electrode 618. As shown in FIG. 10, in an electrode 618 in the Y-axis direction of the position detecting sensor 600, a transparent conductor having a given width is formed so as to have a bent shape (zigzag shape) with a predetermined inclination with respect to the Y-axis direction. As a result, in Patent Document 3, it is possible to either decrease or prevent the Moire effect between the disposition of the pixels in the Y-axis direction, and the electrodes in the Y-axis direction of the position detecting sensor.